Two component coating compositions and coatings produced therefrom

ABSTRACT

The present invention is directed to two component coating compositions that cure under ambient conditions and more particularly to those having low VOC (volatile organic content) that are suitable for use in automotive refinish and Original Equipment Manufacturing (OEM) applications. The coating composition includes crosslinkable and crosslinking components, wherein the crosslinkable component includes a low polydispersity, low molecular weight copolymer having on an average 2 to 25 crosslinkable functional groups, such as hydroxyl, acetoacetoxy, carboxyl, epoxy, primary amine and secondary amine. The copolymer is polymerized from a monomer mixture that includes one or more non-functional methacrylate monomers and one or more functional acrylate monomers provided with the functional groups. The crosslinking component includes polyisocyanate, polyamine, epoxy, polyacid, ketimine, melamine, or a combination thereof. The invention is also directed to coating produced from the coating composition.

FIELD OF INVENTION

This invention generally relates to curable coating compositions used inautomotive refinish and Original Equipment Manufacturing (OEM)applications and it particularly relates to two component coatingcompositions that cure under ambient conditions and more particularly tothose compositions having low VOC (volatile organic content).

BACKGROUND OF THE INVENTION

A number of clear and pigmented coating compositions are utilized invarious coatings, such as, for example, basecoats and clearcoats used inautomotive refinish coatings, which are generally solvent based.

In repairing damage, such as dents to auto bodies, the original coatingin and around the damaged area is typically sanded or ground out bymechanical means. Some times the original coating is stripped off from aportion or off the entire auto body to expose the bare metal underneath.After repairing the damage, the repaired surface is coated, preferablywith low VOC coating compositions, typically in portable or permanentlow cost painting enclosures vented to atmosphere to remove the organicsolvents from the freshly applied paint coatings in a safe manner fromthe standpoint of operator health and explosion hazard. Typically, thedrying and curing of the freshly applied paint takes place within theseenclosures. Furthermore, the foregoing drying and curing steps takeplace within the enclosure to also prevent the wet paint from collectingdirt in the air or other contaminants.

As these paint enclosures take up significant floor space of typicalsmall auto body paint repair shops, these shops prefer to dry and curethese paints as fast as possible. More expensive enclosures arefrequently provided with heat sources, such as conventional heat lampslocated inside the enclosure to cure the freshly applied paint ataccelerated rates. Therefore, to provide more cost effective utilizationof shop floor space and to minimize fire hazards resulting from wetcoatings from solvent based coating compositions, there exists acontinuing need for fast curing coating formulations which cure underambient conditions while still providing outstanding performancecharacteristics particularly chip resistance, mar-resistance, durabilityand appearance.

In the past, several approaches have been used to improve theproductivity of isocyanate crosslinked coatings. One approach was basedon using higher Tg acrylic polymers (U.S. Pat. No. 5,279,862 and5,314,953) and another on the use of reactive oligomers (U.S. Pat. No.6,221,494 B1). Due to the high Mw and high Tg of such acrylic polymers,the fast dry was achievable, but the film vitrified and the faster curewas not achievable. The viscosity of these types of acrylic polymers wasalso comparatively high and thus that approach resulted in higher VOC.The reactive oligomer approach improved the appearance and the rate ofcure of the coating at lower VOC, however these oligomers are difficultto make at high enough Tg needed to reduce the dry time. Moreover, thehigher the amount of these oligomers in the coating compositions, thelower was the hardness of the resultant coatings.

Thus, a continuing need still exists for a coating composition thatcures under ambient conditions, more particularly those compositionshaving low VOC.

STATEMENT OF THE INVENTION

The present invention is directed to a coating composition comprisingcrosslinkable and crosslinking components, wherein said crosslinkablecomponent comprises:

-   -   a copolymer having on an average 2 to 25 crosslinkable groups        selected from the group consisting of hydroxyl, acetoacetoxy,        carboxyl, epoxy, primary and secondary amine, and a combination        thereof; a weight average molecular weight ranging from about        1000 to 4500; a polydispersity ranging from about 1.05 to 2.5;        wherein said copolymer is polymerized from a monomer mixture        comprising one or more non-functional methacrylate monomers and        one or more functional acrylate monomers provided with said        functional groups, and    -   wherein said crosslinking component for said crosslinkable        groups is selected from the group consisting of polyisocyanate,        polyamine, ketimine, melamine, epoxy, polyacid and a combination        thereof.

The present invention is further directed to a process for producing acoating on a substrate, said process comprises:

-   -   a) mixing a crosslinkable and crosslinking components of a        coating composition to form a potmix, wherein said crosslinkable        component comprises:    -   a copolymer having on an average 2 to 25 crosslinkable groups        selected from the group consisting of hydroxyl, acetoacetoxy,        carboxyl, epoxy, primary and secondary amine, and a combination        thereof; a weight average molecular weight ranging from about        1000 to 4500; a polydispersity ranging from about 1.05 to 2.5;        wherein said copolymer is polymerized from a monomer mixture        comprising one or more non-functional methacrylate monomers and        one or more functional acrylate monomers provided with said        functional groups, and    -   wherein said crosslinking component for said crosslinkable        groups is selected from the group consisting of polyisocyanate,        polyamine, ketimine, melamine, epoxy, polyacid and a combination        thereof;    -   b) applying a layer of said potmix on said substrate;    -   c) curing said layer into said coating on said substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As used herein:

-   -   “Two-pack coating composition” means a thermoset coating        composition having two components stored in separate containers.        The containers containing the two components are typically        sealed to increase the shelf life of the components of the        coating composition. The components are mixed just prior to use        to form a pot mix, which has a limited pot life, typically        ranging from a few minutes (15 minutes to 45 minutes) to a few        hours (4 hours to 8 hours). The pot mix is applied as a layer of        a desired thickness on a substrate surface, such as an auto        body. After application, the layer dries and cures at ambient or        elevated temperatures to form a coating on the substrate surface        having desired coating properties, such as, high gloss,        mar-resistance and resistance to environmental etching.

“Low VOC coating composition” means a coating composition that includesthe range of from 0.1 kilograms (1.0 pounds per gallon) to 0.72kilograms (6.0 pounds per gallon), preferably 0.3 kilograms (2.6 poundsper gallon) to 0.6 kilograms (5.0 pounds per gallon) and more preferably0.34 kilograms (2.8 pounds per gallon) to 0.53 kilograms (4.4 pounds pergallon) of the solvent per liter of the coating composition. All VOC'sdetermined under the procedure provided in ASTM D3960.

“High solids composition” means a coating composition having solidcomponent of above 30 percent, preferably in the range of from 35 to 90percent and more preferably in the range of from 40 to 80 percent, allin weight percentages based on the total weight of the composition.

“GPC weight average molecular weight” means a weight average molecularweight measured by utilizing gel permeation chromatography. A highperformance liquid chromatograph (HPLC) supplied by Hewlett-Packard,Palo Alto, Calif. was used. Unless stated otherwise, the liquid phaseused was tetrahydrofuran and the standard was polymethyl methacrylate orpolystyrene.

“Tg” (glass transition temperature) measured in ° C. determined by DSC(Differential Scanning Calorimetry).

“Polydispersity” means GPC weight average molecular weight divided byGPC number average molecular weight. The lower the polydispersity(closer to 1), the narrower will be the molecular weight distribution,which is desired.

“(Meth)acrylate” means acrylate and methacrylate.

“Polymer solids” or “Binder solids” means a polymer or binder in its drystate.

“Crosslinkable component” means a component that includes a compound,polymer or copolymer having functional crosslinkable groups positionedin the backbone of the polymer, pendant from the backbone of thepolymer, terminally positioned on the backbone of the polymer, or acombination thereof. One of ordinary skill in the art would recognizethat certain crosslinkable group combinations would be excluded from thecrosslinkable component of the present invention, since, if present,these combinations would crosslink among themselves (self-crosslink),thereby destroying their ability to crosslink with the crosslinkinggroups in the crosslinking components defined below.

“Crosslinking component” is a component that includes a compound,polymer or copolymer having crosslinking groups positioned in thebackbone of the polymer, pendant from the backbone of the polymer,terminally positioned on the backbone of the polymer, or a combinationthereof, wherein these groups are capable of crosslinking with thecrosslinkable groups on the crosslinkable component (during the curingstep) to produce a coating in the form of crosslinked structures. One ofordinary skill in the art would recognize that certain crosslinkinggroup/crosslinkable group combinations would be excluded from presentinvention, since they would fail to crosslink and produce the filmforming crosslinked structures.

In coating application, especially the automotive refinish application,a key driver is productivity, i.e., the ability of a layer of a coatingcomposition to dry rapidly to a tack free state and then curesufficiently rapidly to a buffable state. However, the productivity isadversely impacted by the increasingly stricter environmentalconsiderations, which require coating compositions to have lower VOCs.The present invention addresses the forgoing issues by utilizingcrosslinking technology. Thus, the present coating composition includesa crosslinkable and crosslinking component.

The crosslinkable component includes a copolymer having on an average 2to 25, preferably 3 to 15, more preferably 4 to 12 crosslinkable groupsselected from the group consisting of hydroxyl, acetoacetoxy, carboxyl,epoxy, primary and secondary amine, and a combination thereof. Thehydroxyl, acetoacetoxy and secondary amine functional groups arepreferred and hydroxyl is more preferred. It would be clear to oneordinary skill in the art that certain combinations would be excludedfrom the foregoing as they tend to self-crosslink. Therefore, acombination of carboxyl, primary or secondary amine and epoxy ascrosslinkable groups would be excluded from the forgoing combinations.The weight average molecular weight of the copolymer ranges from about1000 to 4500, preferably from 1250 to 3700 and more preferably from 1500to 3500, a polydispersity ranging from about 1.05 to 2.5, preferablyranging from 1.1 to 2.0 and more preferably ranging from 1.1 to 1.7. TheTg of the copolymer can range from about −10° C. to 80° C., preferablyfrom about 0° C. to 65° C. and more preferably from about 10° C. to 60°C.

The copolymer is polymerized from a monomer mixture of one or morenon-functional methacrylate monomers and one or more functional acrylatemonomers. The ratio of the non-functional methacrylate monomers to thefunctional acrylate monomers in the monomer mixture ranges from about90:10::10:90, preferably from about 25:75::75:25. Generally, the monomermixture includes 100% to 60%, preferably 100% to 80% of the total amountof the non-functional methacrylate monomers and functional acrylatemonomers, all percentages being in weight percent based on the weight ofthe monomer mixture.

The use of non-functional methacrylate monomers and functional acrylatemonomers in the monomer mixture by the polymerization process describedbelow ensures functionality on almost every copolymer chain, with lowlevels of non-functional chains of preferably less than 1% andmono-functional polymer chains of preferably less than 5%, even at theselow molecular weights, the percentages being based on of the totalnumber of chains. By contrast, using the commonly practiced randompolymerization techniques; the conventional copolymers at these lowmolecular weights would typically have unacceptable functionalitydistribution and contain high levels of undesirable non-functional andmono-functional polymer chains. Generally, the presence ofnon-functional and mono-functional polymer chains in coatingcompositions reduces the crosslinking of the crosslinkablefunctionalities with the crosslinking functionalities and results inpoor coating properties, such as low crosslink density, high solublefraction, low hardness, poor adhesion; and poor chip and humidityresistance.

More particularly, when the copolymers of the present invention have aTg of greater than 10° C. by using suitably appropriate monomers, theresulting coating composition has desirable application viscosity,reactivity and functionality in almost every polymer chain. As a result,a coating from such a composition has improved cure time and desirablecoating properties, such as coating hardness. Since the presence of thecopolymer in coating compositions provides a desirable balance ofcoating properties, much higher levels of these copolymers can beincluded in the coating compositions. As a result, the VOC of theresulting composition, as compared to those containing conventionalreactive oligomers, can be lowered without affecting coating properties.

The non-functional methacrylate monomer can be provided with one or moregroups selected from the group consisting of linear C₁ to C₂₀ alkyl,branched C₃ to C₂₀ alkyl, cyclic C₃ to C₂₀ alkyl, aromatic with 2 to 3rings, phenyl, C₁ to C₂₀ fluorocarbon and a combination thereof. Thefunctional acrylate monomer is provided with one or more groups selectedfrom the group consisting of hydroxyl, acetoacetoxy, primary amine,secondary amine, carboxyl, epoxy and a combination thereof.

Some of the one or more non-functional methacrylate monomers in themonomer mixture include methyl methacrylate, ethyl methacrylate, propylmethacrylate, butyl methacrylate, pentyl methacrylate, hexylmethacrylate, octyl methacrylate, nonyl methacrylate, isodecylmethacrylate, and lauryl methacrylate; branched alkyl monomers, such asisobutyl methacrylate, t-butyl methacrylate and 2-ethylhexylmethacrylate; and cyclic alkyl monomers, such as cyclohexylmethacrylate, methylcyclohexyl methacrylate, trimethylcyclohexylmethacrylate, tertiarybutylcyclohexyl methacrylate and isobornylmethacrylate. Isobornyl methacrylate and iso-butyl methacrylate arepreferred.

Some of the specific functional acrylate monomers in the monomer mixturecan include hydroxyalkyl acrylates, such as hydroxyethyl acrylate,hydroxy propyl acrylate, hydroxyisopropyl acrylate, hydroxybutylacrylate; glycidyl acrylate; acrylic acid; acetoacetoxyethyl acrylateand aminoalkyl acrylates, such as tertiarybutylaminoethyl acrylate andN-methylaminoethyl acrylate. Hydroxyethyl acrylate and hydroxybutylacrylate are preferred.

The monomer mixture can also further include small amounts, typicallyranging from 0.01% to 10% by weight of functional methacrylate monomersprovided enough functional acrylate monomers are present in the monomermixture to ensure the presence of the aforedescribed functionalities oneach polymer chain. All percentages based on the total weight of themonomer mixture.

The monomer mixture can also further include small amounts, typicallyranging from 0.01% to 10% by weight of non-functional acrylate monomers,for example butyl acrylate, provided enough functional acrylate monomersare present in the monomer mixture to ensure the presence of afunctionality on each polymer chain.

The monomer mixture can also include one or more of other monomers forthe purpose of achieving the desired properties, such as hardness,appearance and mar resistance. Some of the other such monomers include,for example, styrene, α-methyl styrene, acrylonitrile andmethacrylonitrile. When included, preferably, the monomer mixtureincludes such monomers in the range of 5% to 30%, all percentages beingin weight percent based on the total weight of the monomer mixture.Styrene is preferred.

If desired one or more silane functionalities can be incorporated intothe copolymers of the present invention preferably by post reactinghydroxyl functionalities on the copolymer with isocyanatopropyltrimethoxy silane. The reaction is conducted on an equivalent basis withequivalents of isocyanate, from the isocyanatopropyl trimethoxy silane,to hydroxyl groups, on the copolymer, ranging from 0.01 to 1.0.

One of the processes of producing the copolymer of the present inventionincludes free radically solution polymerizing the aforedescribed monomermixture at a polymerization temperature ranging from 120° C. to 300° C.,preferably ranging from 150° C. to 200° C. and more preferably rangingfrom 160° C. to 200° C. Typically the reactor gage pressure ranges from0.1 to 2.86 MPa (0 to 400 psig), preferably from 0.1 to 0.71 MPa (0 to100 psig). It is understood that the higher the polymerizationtemperature, the higher will be the reactor pressure for a givencomposition of monomers and solvent. Typically, the monomer mixture issolvated in a polymerization medium, which typically includes one ormore organic solvents, such as methyl amyl ketone, Aromatic 100 fromExxonMobil Chemical, Houston, Tex. and butyl acetate. Thus, the higherthe boiling point of the polymerization medium, the higher can be thepolymerization temperature. Typical reaction time ranges from about 1hour to 6 hours, generally from about 2 hours to 4 hours.

The polymerization of the monomer mixture can be initiated by preferablysimultaneously adding conventional thermal initiators, such as Azosexemplified by Vazo® 64 supplied by DuPont Company, Wilmington, Del.;and peroxides, such as t-butylperoxy acetate. By adjusting the amount ofinitiator used and the reaction temperature, the molecular weight of theresulting copolymer of the present invention can be adjusted. Thus, toattain the same molecular weight, the lower the polymerizationtemperature, the more will be the amount of the initiator needed.Typically, to attain the claimed molecular weight range, at highpolymerization temperatures (higher than 150° C.) about 0.1% to about 6%of initiator is used, all percentages being in weight percent based onthe weight of the monomer mixture. Conversely, at low polymerizationtemperatures (lower than 150° C.) about 4% to about 12% of initiator isused, all percentages being in weight percent based on the weight of themonomer mixture. Another approach to lowering the molecular weight ofthe copolymer includes polymerizing the monomer mixture under verydilute conditions. Thus, using the same amount of the initiator, acopolymer made at 70 weight percent solids will have higher molecularweight than a copolymer made at 10 to 20 weight percent solids.

One of the processes for incorporating acetoacetoxy functionalities inthe copolymer can be to post react some or all of the hydroxylfunctionalities on the copolymer with tertiary butyl acetoacetate.

The crosslinking component of the present invention suitable forcrosslinking with the crosslinkable groups present in the copolymer inthe crosslinking component is selected from the group consisting ofpolyisocyanate, polyamine, ketimine, melamine, epoxy, polyacid and acombination thereof. It would be clear to one ordinary skill in the artthat generally certain combinations of crosslinking groups fromcrosslinking components crosslink with crosslinkable groups from thecrosslinkable components. Some of those paired combinations include:

-   -   1. Ketimine crosslinking component generally crosslinks with        acetoacetoxy crosslinkable groups.    -   2. Polyisocyanate and melamine crosslinking components generally        crosslink with hydroxyl, primary and secondary amine        crosslinkable groups.    -   3. Epoxy crosslinking component generally crosslinks with        carboxyl, primary and secondary amine crosslinkable groups.    -   4. Polyamine crosslinking component generally crosslinks with        acetoacetoxy crosslinkable groups.    -   5. Polyacid crosslinking component generally crosslinks with        epoxy crosslinkable groups.

However, it should be noted that combinations of the foregoing pairedcombinations could also be used.

Typically, the polyisocyanate is provided with in the range of 2 to 10,preferably 2.5 to 8, more preferably 3 to 5 isocyanate functionalities.Generally, the ratio of equivalents of isocyanate functionalities on thepolyisocyanate per equivalent of the functional group of the copolymerranges from 0.5/1 to 3.0/1, preferably from 0.7/1 to 1.8/1, morepreferably from 0.8/1 to 1.3/1. Some suitable polyisocyanates includearomatic, aliphatic, or cycloaliphatic polyisocyanates, trifunctionalpolyisocyanates and isocyanate functional adducts of a polyol anddifunctional isocyanates. Some of the particular polyisocyanates includediisocyanates, such as 1,6-hexamethylene diisocyanate, isophoronediisocyanate, 4,4′-biphenylene diisocyanate, toluene diisocyanate,biscyclohexyl diisocyanate, tetramethyl-m-xylylene diisocyanate, ethylethylene diisocyanate, 1-methyltrimethylene diisocyanate, 1,3-phenylenediisocyanate, 1,5-napthalene diisocyanate,bis-(4-isocyanatocyclohexyl)-methane and 4,4′-diisocyanatodiphenylether.

Some of the suitable trifunctional polyisocyanates includetriphenylmethane triisocyanate, 1,3,5-benzene triisocyanate, and2,4,6-toluene triisocyanate. Trimers of diisocyanate, such as the trimerof hexamethylene diisocyanate sold under the trademark Desmodur®N-3390by Bayer Corporation of Pittsburgh, Pa. and the trimer of isophoronediisocyanate are also suitable. Furthermore, trifunctional adducts oftriols and diisocyanates are also suitable. Trimers of diisocyanates arepreferred and trimers of isophorone and hexamethylene diisocyanates aremore preferred.

Some of the suitable melamines include monomeric melamine, polymericmelaminelformaldehyde resin or a combination thereof. The coatingcomposition can include in the range of from 0.1 percent to 40%,preferably in the range of from 15% to 35%, and most preferably in therange of 20 percent to 30 percent of the melamine, the percentages beingin weight percentages based on the total weight of composition solids.The monomeric melamines include low molecular weight melamines whichcontain, on an average, three or more methylol groups etherized with aC₁ to C₅ monohydric alcohol such as methanol, n-butanol, or isobutanolper triazine nucleus, and have an average degree of condensation up toabout 2 and preferably in the range of about 1.1 to about 1.8, and havea proportion of mononuclear species not less than about 50 percent byweight. By contrast the polymeric melamines have an average degree ofcondensation of more than 1.9. Some such suitable monomeric melaminesinclude alkylated melamines, such as methylated, butylated, isobutylatedmelamines and mixtures thereof. Many of these suitable monomericmelamines are supplied commercially. For example, Cytec Industries Inc.,West Patterson, N.J. supplies Cymel® 301 (degree of polymerization of1.5,95% methyl and 5% methylol), Cymel® 350 (degree of polymerization of1.6,84% methyl and 16% methylol), 303, 325, 327 and 370, which are allmonomeric melamines. Suitable polymeric melamines include high imino(partially alkylated, —N, —H) melamine known as Resimene® BMP5503(molecular weight 690, polydispersity of 1.98, 56% butyl, 44% imino),which is supplied by Solutia Inc., St. Louis, Mo., or Cymel® 1158provided by Cytec Industries Inc., West Patterson, N.J. Cytec IndustriesInc. also supplies Cymel® 1130 @ 80 percent solids (degree ofpolymerization of 2.5), Cymel® 1133 (48% methyl, 4% methylol and 48%butyl), both of which are polymeric melamines.

Ketimines useful in the present invention are typically prepared by thereaction of ketones with amines. Representative ketones, which may beused to form the ketimine, include acetone, methyl ethyl ketone, methylisopropyl ketone, methyl isobutyl ketone, diethyl ketone, benzylmethylketone, diisopropyl ketone, cyclopentanone, and cyclohexanone.Representative amines which may be used to form the ketimine includeethylene diamine, ethylene triamine, propylene diamine, tetramethylenediamine, 1,6-hexamethylene diamine, bis(6-aminohexyl)ether,tricyclodecane diamine, N,N′-dimethyldiethyltriamine,cyclohexyl-1,2,4-triamine, cyclohexyl-1,2,4,5-tetraamine,3,4,5-triaminopyran, 3,4-diaminofuran, and cycloaliphatic diamines.Preparation and other suitable imines are shown in U.S. Pat. No.6,297,320, incorporated herein by reference. It should be noted thatwhen the copolymer contains only acetoacetoxy functional groups, thenketimine is typically utilized as a crosslinking component.

Suitable polyamines include primary and secondary amines, such as,ethylenediamine, propylenediamine, butylenediamine,pentamethylenediamine, hexamethylenediamine, decamethylenediamine,4,7-dioxadecane-1,10-diamine, dodecamethylenediamine,4,9-dioxadodecane-1,12-diamine,7-methyl-4,10-dioxatridecane-1,13-diamine, 1,2-diaminocyclohexane,1,4-diaminocyclohexane, 4,4′-diminodicyclohexyl methane, isophoronediamine, bis(3-methyl-4-aminocyclohexyl)methane,2,2-bis(4-aminocyclohexyl)propane, nitrile tris(ethane amine),bis(3-aminopropyl)methylamine, 3-amino-1-(methylamino)propane,3-amino-1-(cyclohexylamino)propane, and N-(2-hydroxyethyl)ethylenediamine. Ethylenediamine, propylenediamine, butylenediamine and1,2-diaminocyclohexane are preferred.

Suitable epoxy crosslinking components contain at least two glycidylgroups and can be an oligomer or a polymer, such as sorbitolpolyglycidyl ether, mannitol polyglycidyl ether, pentaerythritolpolyglycidol ether, glycerol polyglycidyl ether, low molecular weightepoxy resins, such as epoxy resins of epichlorohydrin and bisphenol A.,di- and polyglycidyl esters of acids, polyglycidyl ethers ofisocyanurates, such as Denacol® EX301 from Nagase. Sorbitol polyglycidylether, such as Araldite XYGY-358® from Ciba-Geigy, and di- andpolyglycidyl esters of acids, such as Araldite CY-184® from Ciba-Geigy,are preferred since they form high quality finishes.

Suitable polyacid crosslinking components include aliphatic acids, suchas succinic, maleic, fumaric, glutaric, adipic, azeleic, and sebacicacids; cycloaliphatic polycarboxylic acids, such as tetrahydrophthalicacid, hexahydrophthalic acid, 1,2-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid,cyclohexanetetracarboxylic acid and cyclobutanetetracarboxylic acid;aromatic polycarboxylic acids, such as phthalic acid, isophthalic acid,terephthalic acid, halogenophthalic acids, such as, tetrachloro- ortetrabromophthalic acid, trimellitic acid, and pyromellitic acid. Itshould be noted that aromatic acid crosslinkers tend to be less durablein clearcoats than aliphatic and cycloaliphatic acid crosslinkers.

The coating composition preferably includes a catalytic amount of acatalyst for accelerating the curing process. Generally, in the range ofabout 0.001 percent to about 5 percent, preferably in the range of from0.005 percent to 2 percent, more preferably in the range of from 0.01percent to 1 percent of the catalyst is utilized, all in weight percentbased on the total weight of crosslinkable and crosslinking componentsolids. A wide variety of catalysts can be used, such as, tin compounds,including dibutyl tin dilaurate and dibutyl tin diacetate; tertiaryamines, such as, triethylenediamine. These catalysts can be used aloneor in conjunction with carboxylic acids, such as, acetic acid. One ofthe commercially available catalysts, sold under the trademark, Fastcat®4202 dibutyl tin dilaurate by Elf-Atochem North America, Inc.Philadelphia, Pa., is particularly suitable.

When the crosslinking component includes melamine, it also preferablyincludes one or more acid catalysts to further enhance the crosslinkingof the components on curing. Generally, the coating composition includesin the range of from 0.1 percent to 5 percent, preferably in the rangeof from 0.1 to 2 percent, more preferably in the range of from 0.5percent to 2 percent and most preferably in the range of from 0.5percent to 1.2 percent of the catalyst, the percentages being in weightpercentage based on the total weight of composition solids. Somesuitable catalysts include the conventional acid catalysts, such asaromatic sulfonic acids, for example dodecylbenzene sulfonic acid,para-toluenesulfonic acid and dinonyinaphthalene sulfonic acid, all ofwhich are either unblocked or blocked with an amine, such as dimethyloxazolidine and 2-amino-2-methyl-1-propanol, n,n-dimethylethanolamine ora combination thereof. Other acid catalysts that can be used are strongacids, such as phosphoric acids, more particularly phenyl acidphosphate, which may be unblocked or blocked with an amine.

The crosslinkable component of the present invention can further includein the range of from 0.1 percent to 95 percent, preferably in the rangeof from 10 percent to 90 percent, more preferably in the range of from20 percent to 80 percent and most preferably in the range of 30 percentto 70 percent, all based on the total weight of the crosslinkablecomponent of an additional acrylic polymer, a polyester or a combinationthereof. Applicants have discovered that by adding one or more of theforegoing polymers to the crosslinkable component, the coatingcomposition resulting therefrom provides coating with improved sagresistance, and flow and leveling properties.

The additional acrylic polymer suitable for use in the present inventioncan have a GPC weight average molecular weight exceeding 5000,preferably in the range of from 5000 to 20,000, more preferably in therange of 6000 to 20,000, and most preferably in the range of from 8000to 12,000. The Tg of the acrylic polymer varies in the range of from 0°C. to 100° C., preferably in the range of from 30° C. to 80° C.

The additional acrylic polymer suitable for use in the present inventioncan be conventionally polymerized from typical monomers, such as alkyl(meth)acrylates having alkyl carbon atoms in the range of from 1 to 18,preferably in the range of from 1 to 12 and styrene and functionalmonomers, such as, hydroxyethyl acrylate and hydroxyethyl methacrylate.

The polyester suitable for use in the present invention can have a GPCweight average molecular weight exceeding 1500, preferably in the rangeof from 1500 to 100,000, more preferably in the range of 2000 to 50,000,still more preferably in the range of 2000 to 8000 and most preferablyin the range of from 2000 to 5000. The Tg of the polyester varies in therange of from −50° C. to +100° C., preferably in the range of from −20°C. to +50° C.

The polyester suitable for use in the present invention can beconventionally polymerized from suitable polyacids, includingcycloaliphatic polycarboxylic acids, and suitable polyols, which includepolyhydric alcohols. Examples of suitable cycloaliphatic polycarboxylicacids are tetrahydrophthalic acid, hexahydrophthalic acid,1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid,1,4-cyclohexanedicarboxylic acid, 4-methylhexahydrophthalic acid,endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid,endoethylenehexahydrophthalic acid, camphoric acid,cyclohexanetetracarboxylic acid and cyclobutanetetracarboxylic acid. Thecycloaliphatic polycarboxylic acids can be used not only in their cisbut also in their trans form and as a mixture of both forms. Examples ofsuitable polycarboxylic acids, which, if desired, can be used togetherwith the cycloaliphatic polycarboxylic acids, are aromatic and aliphaticpolycarboxylic acids, such as, for example, phthalic acid, isophthalicacid, terephthalic acid, halogenophthalic acids, such as, tetrachloro-or tetrabromophthalic acid, adipic acid, glutaric acid, azelaic acid,sebacic acid, fumaric acid, maleic acid, trimellitic acid, andpyromellitic acid.

Suitable polyhydric alcohols include ethylene glycol, propanediols,butanediols, hexanediols, neopentylglycol, diethylene glycol,cyclohexanediol, cyclohexanedimethanol, trimethylpentanediol,ethylbutylpropanediol, ditrimethylolpropane, trimethylolethane,trimethylolpropane, glycerol, pentaerythritol; dipentaerythritol,tris(hydroxyethyl) isocyanate, polyethylene glycol and polypropyleneglycol. If desired, monohydric alcohols, such as, for example, butanol,octanol, lauryl alcohol, ethoxylated or propoxylated phenols may also beincluded along with polyhydric alcohols. The details of polyestersuitable for use in the present invention are further provided in theU.S. Pat. No. 5,326,820, which is incorporated herein by reference. Onecommercially available polyester, which is particularly preferred, isSCD®-1040 polyester, which is supplied by Etna Product Inc., ChagrinFalls, Ohio.

The crosslinkable component of the present invention can be blended withreactive oligomers covered in U.S. Pat. No. 6,221,494, whichincorporated herein by reference and non-alicyclic (linear or aromatic)oligomers, if desired. Such non-alicyclic-oligomers can be made by usingnon-alicyclic anhydrides, such as succinic or phthalic anhydrides, ormixtures thereof. Caprolactone oligomers described in U.S. Pat. No.5,286,782, incorporated herein by reference, can also be used.

The coating composition of the present invention can optionally contain,in the range of from 0.1 percent to 50 percent, a modifying resin, suchas non-aqueous dispersion (NAD), all percentages being based on thetotal weight of composition solids. The weight average molecular weightof the modifying resin generally varies in the range of from 20,000 to100,000, preferably in the range of from 25,000 to 80,000 and morepreferably in the range from 30,000 to 50,000.

The non-aqueous dispersion-type polymer is prepared by dispersionpolymerizing at least one vinyl monomer in the presence of a polymerdispersion stabilizer and an organic solvent. The polymer dispersionstabilizer may be any of the known stabilizers used commonly in thefield of non-aqueous dispersions.

The coating composition can optionally include in the range of from 0.1percent to 30 percent, preferably in the range of from 5 percent to 25percent, more preferably in the range of from 10 percent to 20 percent,all in weight percentages based on the total weight of componentssolids, additional crosslinkers, such as aldimine and polyasparticesters. Aldimines useful in the present invention may be prepared fromaldehydes, such as acetaldehyde, formaldehyde, propionaldehyde,isobutyraldehyde, n-butyraldehyde, heptaldehyde and cyclohexyl aldehydesby reaction with amine. Representative amines which may be used to formthe aldimine include ethylene diamine, ethylene triamine, propylenediamine, tetramethylene diamine, 1,6-hexamethylene diamine,bis(6-aminohexyl)ether, tricyclodecane diamine,N,N′-dimethyldiethyltriamine, cyclohexyl-1,2,4-triamine,cyclohexyl-1,2,4,5-tetraamine, 3,4,5-triaminopyran, 3,4-diaminofuran,and cycloaliphatic diamines.

Polyaspartic esters useful in the present invention are typicallyprepared by the reaction of diamines, such as, isophorone diamine withdialkyl maleates, such as, diethyl maleate.

The foregoing polyaspartic ester and selected aldimines are suppliedcommercially under the trademark Desmophen® amine co-reactants by BayerCorporation, Pittsburgh, Pa. Suitable catalyst for the crosslinkreaction of aldimine and aspartic ester with acetoxy functionality issold under the trademark Amicure® TEDA from Air Products & Chemicals,Allentown, Pa.

The crosslinkable or crosslinking component of coating composition ofthe present invention, typically contains at least one organic solventwhich is typically selected from the group consisting of aromatichydrocarbons, such as, petroleum naphtha or xylenes; ketones, such as,methyl amyl ketone, methyl isobutyl ketone, methyl ethyl ketone oracetone; esters, such as, butyl acetate or hexyl acetate; and glycolether esters. such as propylene glycol monomethyl ether acetate. Theamount of organic solvent added depends upon the desired solids level aswell as the desired amount of VOC of the composition. If desired, theorganic solvent may be added to both components of the binder. Highsolids and low VOC coating composition is preferred.

The coating composition of the present invention can also containconventional additives, such as, pigments, metallic flakes, hollow glassbeads, UV absorbers, stabilizers, rheology control agents, flow agents,reinforcing fibers, toughening agents and fillers. Such additionaladditives will, of course, depend upon the intended use of the coatingcomposition. Fillers, pigments, and other additives that would adverselyaffect the clarity of the cured coating are typically not included ifthe composition is intended as a clear coating. It is understood thatone or more of these conventional additives, such as pigments, can beadded before, during or at the end of the agitating step.

To improve weatherability of the coating from the coating composition,about 0.1 to 5% by weight, based on the weight of the compositionsolids, of an ultraviolet light stabilizer or a combination ofultraviolet light stabilizers and absorbers may be added. Thesestabilizers include ultraviolet light absorbers, screeners, quenchersand specific hindered amine light stabilizers. Also, about 0.1 to 5% byweight, based on the weight of the composition solids, of an antioxidantcan be added. Most of the foregoing stabilizers are supplied by CibaSpecialty Chemicals, Tarrytown, N.Y.

The coating composition of the present invention can be formulated inthe form of a clear coating composition, pigmented composition,metallized coating composition, basecoat composition, monocoatcomposition or a primer. The present formulations are particularlyuseful as a clear coating for outdoor articles, such as automobile andother vehicle body parts. The substrate is generally prepared with aprimer and or a color coat or other surface preparation prior to coatingwith the present compositions.

The present invention is also directed to a method of producing acoating on a substrate. The coating composition of the present inventioncan be supplied in the form of a two-pack coating composition.Generally, the crosslinkable component and the crosslinking componentare mixed-typically just prior to application to form a pot mix. Themixing can take place though a conventional mixing nozzle or separatelyin a container. A layer of the pot mix generally having a thickness inthe range of 15 micrometers to 200 micrometers is applied over asubstrate, such as an automotive body or an automotive body that hasprecoated layers, such as electrocoat primer. The foregoing applicationstep can be conventionally accomplished by spraying, electrostaticspraying, roller coating, dipping or brushing the pot mix over thesubstrate. The layer after application is typically dried to reduce thesolvent content from the layer and then cured at temperature rangingfrom ambient to 204° C. Under typical automotive OEM applications, thedried layer of the composition can be typically cured at elevatedtemperatures ranging from 60° C. to 160° C. in about 10 to 60 minutes.Preferably, for automotive refinish applications curing can take placeat about ambient to 60° C., and for heavy-duty truck body applicationsit can take place at about 60° C. to 80° C. The cure under ambientconditions occurs in about 30 minutes to 24 hours, generally in about 30minutes to 4 hours to form, a coating on the substrate having thedesired coating properties. It is further understood that the actualcuring time can depend upon the thickness of the applied layer, the curetemperature, humidity and on any additional mechanical aids, such asfans, that assist in continuously flowing air over the coated substrateto accelerate the cure rate. It is understood that actual curingtemperature would vary depending upon the catalyst and the amountthereof, thickness of the layer being cured and the amount of thecrosslinking component utilized.

The suitable substrates for applying the coating composition of thepresent invention include automobile bodies, any and all itemsmanufactured and painted by automobile sub-suppliers, frame rails,commercial trucks and truck bodies, including but not limited tobeverage bodies, utility bodies, ready mix concrete delivery vehiclebodies, waste hauling vehicle bodies, and fire and emergency vehiclebodies, as well as any potential attachments or components to such truckbodies, buses, farm and construction equipment, truck caps and covers,commercial trailers, consumer trailers, recreational vehicles, includingbut not limited to, motor homes, campers, conversion vans, vans,pleasure vehicles, pleasure craft snow mobiles, all terrain vehicles,personal watercraft, bicycles, motorcycles, boats, and aircraft. Thesubstrate further includes industrial and commercial new constructionand maintenance thereof;

cement and wood floors; walls of commercial and residential structures,such office buildings and homes; amusement park equipment; concretesurfaces, such as parking lots and drive ways; asphalt and concrete roadsurface, wood substrates, marine surfaces; outdoor structures, such asbridges, towers; coil coating; railroad cars; printed circuit boards;machinery; OEM tools; signage; fiberglass structures; sporting goods;and

sporting equipment.

EXAMPLES Test Procedures

Swell Ratio

The swell ratio of a free film (removed from a sheet ofTPO-thermoplastic olefin) was determined by swelling the film inmethylene chloride. The free film was placed between two layers ofaluminum foil and using a LADD punch, a disc of about 3.5 mm in diameterwas punched out of the film and the foil was removed from the film. Thediameter of the unswollen film (D_(o)) was measured using a microscopewith a 10× magnification and a filar lens. Four drops of methylenechloride were added to the film and the film was allowed to swell for afew seconds and then a glass slide was placed over the film and theswollen film diameter (D_(s)) was measured. The swell ratio was thencalculated as follow:Swell ratio=(D _(s))²/(D _(o))²

The lower the swell ratio, the higher is the crosslink density.

Persoz Hardness Test

The change in film hardness of the coating was measured with respect totime by using a Persoz hardness tester Model No. 5854 (ASTM D4366),supplied by Byk-Mallinckrodt, Wallingford, Conn. The numbers ofoscillations (referred to as Persoz number) were recorded.

Hardness (Fischer)

Hardness was measured using a Fischerscope® hardness tester (themeasurement is in Newtons per square millimeter).

Cotton Tack Free Time

Allow coated panel to dry for set period of time (e.g. 30 minutes). Dropa cotton ball from a height of 1 inch onto the surface of the panel andleave the cotton ball on the surface for a set time interval and invertpanel. Repeat above until the time the cotton ball drops off the panelon inversion and note that as the cotton tack free time.

BK Dry Time

Surface drying times of coated panels measured according to ASTM D5895.

Gel Fraction

Measured according to the procedure set forth in U.S. Pat. No.6,221,494, column 8, line 56 to column 9, line 2, which procedure ishereby incorporated by reference.

MEK Rubs

A coated panel is rubbed (100 times) with an MEK (methyl ethyl ketone)soaked cloth using a rubbing machine and any excess MEK is wiped off.The panel is rated from 1-10. Rating 10—no visible damage to thecoating, rating 9—1-3 distinct scratches, rating 8—4-6 distinctscratches, rating 7—7-10 distinct scratches, rating 6—10-15 distinctscratches with slight pitting or slight loss of color, rating 5—15-20distinct scratches with slight to moderate pitting or moderate loss ofcolor, rating 4—scratches start to blend into one another, rating 3—onlya few undamaged areas between blended scratches, rating 2—no visiblesigns of undamaged paint, rating 1 complete failure—bare spots areshown. The final rating is obtained by multiplying the number of rubs bythe rating.

Water Spot Test

Water spot rating is a measure of how well the film is crosslinked earlyin the curing of the film. If water spot damage is formed on the film,this is an indication that the cure is not complete and further curingof the film is needed before the film can be wet sanded or buffed ormoved from the spray both. The water spot rating is determined in thefollowing manner.

Coated panels are laid on a flat surface and deionized water was appliedwith a pipette at 1 hour-timed intervals. A drop about ½ inch indiameter was placed on the panel and allowed to evaporate. The spot onthe panel was checked for deformation and discoloration. The panel waswiped lightly with cheesecloth wetted with deionized water, which wasfollowed by lightly wiping the panel dry with the cloth. The panel wasthen rated on a scale of 1 to 10. Rating of 10 best—no evidence ofspotting or distortion of discoloration, rating 9—barely detectable,rating 8—slight ring, rating 7—very slight discoloration or slightdistortion, rating 6—slight loss of gloss or slight discoloration,rating 5—definite loss of gloss or discoloration, rating of 4—slightetching or definite distortion, rating of 3—light lifting, bad etchingor discoloration, rating of 2—definite lifting and rating of1—dissolving of the film.

Copolymer 1

To a 1-liter flask fitted with heating mantle, stirrer, monomer andinitiator feed lines, an initial solvent charge of 268.4 grams of xylenewas added. The solvent was heated to 190° C. under 2.5 bar pressure. Amonomer mixture (IBMA/HEA 70/30) of 2489.9 g of isobutyl methacrylate(IBMA from Lucite International, Inc. Cordova, Tenn.), 1067.1 g ofhydroxyl ethyl acrylate (Rorcryl 420® HEA from Rohm and Haas,Philadelphia, Pa.) and 33.3 g of xylene as solvent was added to theflask over a period of 240 minutes in such a way that the level in the1-liter flask was held constant at 0.55 liters and the reactor effluentwas fed to an attached 12 liter flask fitted with heating mantle,stirrer, water cooled condenser with nitrogen purge and initiator feedline. Simultaneously with the monomer feed, a mixture of 14.5 g oftert-butylperoxy acetate (Luperox® 7M75 initiator from Atofina,Philadelphia, Pa.) and 803.4 g of xylene was added over a period of 240minutes. Polymerization temperature of 190° C. was maintained over theentire reaction time. After completion of the feeds to the 1-literflask, the flask was drained over 25 minutes into the 12-liter flask.Once transfer from the 1-liter flask to the 12-liter flask began, the12-liter flask was heated to reflux at 140° C. Thirty-four minutes afterthe transfer from the 1-liter flask to the 12-liter flask began, 1.9 gof tert-butyl peroxy acetate (Luperox® 7M75 initiator from Atofina,Philadelphia, Pa.) and 12.0 g of xylene were added all at once to the12-liter flask. Directly thereafter, 17.5 g of tert-butyl peroxy acetate(Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and 108.4 g ofxylene were fed to the 12-liter reactor over 220 minutes. Once theinitiator feed was complete, an additional 19.4 g of Luperox® 7M75initiator and 139.1 g of xylene were fed over half an hour. The 12-literflask was held at reflux for 1 hour and cooled to 80° C. An additional84.6 g of xylene were added to the 12-liter flask and the batch filledout.

The resulting copolymer@ 65.3% solids had a GPC Mn of 2099 and GPC Mw of2991. The copolymer had an average number of 2.6 hydroxyl groups fromthe hydroxy ethyl acrylate per polymer chain. The Tg of the copolymerwas −16.5° C., using dynamic scanning calorimetry.

Copolymer 2

To a 1-liter flask fitted with heating mantle, stirrer, monomer andinitiator feed lines, an initial solvent charge of 268.4 grams of xylenewas added. The solvent was heated to 190° C. under 2.5 bar pressure. Amonomer mixture (IBOMA/IBMA/HEA 35/35/30) of 1244.9 g of isobornylmethacrylate (AGEFLEX® IBOMA from CIBA Specialty Chemicals, High Point,N.C.), 1244.9 g of isobutyl methacrylate (IBMA from LuciteInternational, Inc. Cordova, Tenn.), 1067.1 g of hydroxy ethyl acrylate(Rorcryl 420® HEA from Rohm and Haas, Philadelphia, Pa.) and 33.3 g ofxylene as solvent was added to the flask over a period of 240 minutes insuch a way that the level in the 1-liter flask was held constant at 0.55liters and the reactor effluent was fed to an attached 12 liter flaskfitted with heating mantle, stirrer, water cooled condenser withnitrogen purge and initiator feed line. Simultaneously with the monomerfeed, a mixture of 14.5 g of tert-butylperoxy acetate (Luperox® 7M75initiator from Atofina, Philadelphia, Pa.) and 803.4 g of xylene wasadded over a period of 240 minutes. Polymerization temperature of 190°C. was maintained over the entire reaction time. After completion of thefeeds to the 1-liter flask, the flask was drained over 25 minutes intothe 12-liter flask. Once transfer from the 1-liter flask to the 12-literflask began, the 12-liter flask was heated to reflux at 140° C.Thirty-four minutes after the transfer from the 1-liter flask to the12-liter flask began, 1.9 g of tert-butylperoxy acetate (Luperox® 7M75initiator from Atofina, Philadelphia, Pa.) and 12.0 g of xylene wereadded all at once to the 12-liter flask. Directly thereafter, 17.5 g oftert-butylperoxy acetate (Luperox® 7M75 initiator from Atofina,Philadelphia, Pa.) and 108.4 g of xylene were fed to the 12-literreactor over 220 minutes. Once the initiator feed was complete, anadditional 19.4 g of Luperox® 7M75 initiator and 139.1 g of xylene werefed over half an hour. The 12-liter flask was held at reflux for 1 hourand cooled to 80° C. An additional 84.6 g of xylene were added to the12-liter flask and the batch filled out.

The resulting copolymer@ 65.3% solids had a GPC Mn of 1986 and GPC Mw of2735. The copolymer had an average number of 2.6 hydroxyl groups fromthe hydroxyethyl acrylate per polymer chain. The Tg of the copolymer was5.0° C., using dynamic scanning calorimetry.

Copolymer 3

To a 1-liter flask fitted with heating mantle, stirrer, monomer andinitiator feed lines, an initial solvent charge of 268.4 grams of xylenewas added. The solvent was heated to 175° C. under 2.5 bar pressure. Amonomer mixture (IBOMA/HEA 70/30) of 2489.8 g of isobornyl methacrylate(AGEFLEX® IBOMA from CIBA Specialty Chemicals, High Point, N.C.) and1067.1 g of hydroxy ethyl acrylate (Rorcryl 420® HEA from Rohm and Haas,Philadelphia, Pa.) and 33.3 g of xylene as solvent was added to theflask over a period of 240 minutes in such a way that the level in the1-liter flask was held constant at 0.55 liters and the reactor effluentwas fed to an attached 12 liter flask fitted with heating mantle,stirrer, water cooled condenser with nitrogen purge and initiator feedline. Simultaneously with the monomer feed, a mixture of 14.5 g oftert-butylperoxy acetate (Luperox® 7M75 initiator from Atofina,Philadelphia, Pa.) and 803.4 g of xylene was added over a period of 240minutes. Polymerization temperature of 190° C. was maintained over theentire reaction time. After completion of the feeds to the 1-literflask, the flask was drained over 25 minutes into the 12-liter flask.Once transfer from the 1-liter flask to the 12-liter flask began, the12-liter flask was heated to reflux at 140° C. Thirty-four minutes afterthe transfer from the 1-liter flask to the 12-liter flask began, 1.9 gof tert-butylperoxy acetate (Luperox® 7M75 initiator from Atofina,Philadelphia, Pa.) and 12.0 g of xylene were added all at once to the12-liter flask. Directly thereafter, 17.5 g of tert-butylperoxy acetate(Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and 108.4 g ofxylene were fed to the 12-liter reactor over 220 minutes. Once theinitiator feed was complete, an additional 19.4 g of Luperox® 7M75initiator and 139.1 g of xylene were fed over half an hour. The 12-literflask was held at reflux for 1 hour and cooled to 80° C. An additional84.6 g of xylene were added to the 12-liter flask and the batch filledout.

The resulting copolymer@ 65.6% solids had a GPC Mn of 1935 and GPC Mw of2656. The copolymer had an average number of 2.6 functional groups ofhydroxyethyl acrylate per polymer chain. The Tg of the copolymer was38.6° C., using dynamic scanning calorimetry.

Copolymer 4

To a 1-liter flask fitted with heating mantle, stirrer, monomer andinitiator feed lines, an initial solvent charge of 268.4 grams of xylenewas added. The solvent was heated to 175° C. under 2.5 bar pressure. Amonomer mixture (MMA/HEA 70/30) of 2489.8 g of methyl methacrylate (MMAfrom Lucite International, Inc. Cordova, Tenn.), 1067.1 g of hydroxyethyl acrylate (Rorcryl 420® HEA from Rohm and Haas, Philadelphia, Pa.)and 33.3 g of xylene as solvent was added to the flask over a period of240 minutes in such a way that the level in the 1-liter flask was heldconstant at 0.55 liters and the reactor effluent was fed to an attached12 liter flask fitted with heating mantle, stirrer, water cooledcondenser with nitrogen purge and initiator feed line. Simultaneouslywith the monomer feed, a mixture of 14.5 g of tert-butylperoxy acetate(Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and 803.4 g ofxylene was added over a period of 240 minutes. Polymerizationtemperature of 190° C. was maintained over the entire reaction time.After completion of the feeds to the 1-liter flask, the flask wasdrained over 25 minutes into the 12-liter flask. Once transfer from the1-liter flask to the 12-liter flask began, the 12-liter flask was heatedto reflux at 140° C. Thirty-four minutes after the transfer from the1-liter flask to the 12-liter flask began, 1.9 g of tert-butylperoxyacetate (Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and12.0 g of xylene were added all at once to the 12-liter flask. Directlythereafter, 17.5 g of tert-butylperoxy acetate (Luperox® 7M75 initiatorfrom Atofina, Philadelphia, Pa.) and 108.4 g of xylene were fed to the12-liter reactor over 220 minutes. Once the initiator feed was complete,an additional 19.4 g of Luperox® 7M75 initiator and 139.1 g of xylenewere fed over half an hour. The 12-liter flask was held at reflux for 1hour and cooled to 80° C. An additional 84.6 g of xylene were added tothe 12-liter flask and the batch filled out.

The resulting copolymer@ 65.7% solids had a GPC Mn of 2683 and GPC Mw of4198. The copolymer had an average number of 2.6 functional groups ofhydroxyethyl acrylate per polymer chain. The Tg of the copolymer was27.1° C., using dynamic scanning calorimetry.

Copolymer 5

To a 1-liter flask fitted with heating mantle, stirrer, monomer andinitiator feed lines, an initial solvent charge of 268.4 grams of xylenewas added. The solvent was heated to 185° C. under 3.5 bar pressure. Amonomer mixture (MMA/HEA 70/30) of 2489.8 g of methyl methacrylate (MMAfrom Lucite International, Inc. Cordova, Tenn.), 1067.1 g of hydroxyethyl acrylate (Rorcryl 420® HEA from Rohm and Haas, Philadelphia, Pa.)and 33.3 g of xylene as solvent was added to the flask over a period of240 minutes in such a way that the level in the 1-liter flask was heldconstant at 0.55 liters and the reactor effluent was fed to an attached12 liter flask fitted with heating mantle, stirrer, water cooledcondenser with nitrogen purge and initiator feed line. Simultaneouslywith the monomer feed, a mixture of 14.6 g of tert-butylperoxy acetate(Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and 803.4 g ofxylene was added over a period of 240 minutes. Polymerizationtemperature of 190° C. was maintained over the entire reaction time.After completion of the feeds to the 1-liter flask, the flask wasdrained over 25 minutes into the 12-liter flask. Once transfer from the1-liter flask to the 12-liter flask began, the 12-liter flask was heatedto reflux at 140° C. Thirty-four minutes after the transfer from the1-liter flask to the 12-liter flask began, 1.9 g of tert-blutylperoxyacetate (Luperox® 7M75 initiator from Atofina, Philadelphia, Pa.) and12.0 g of xylene were added all at once to the 12-liter flask. Directlythereafter, 17.5 g of tert-butylperoxy acetate (Luperox® 7M75 initiatorfrom Atofina, Philadelphia, Pa.) and 108.4 g of xylene were fed to the12-liter reactor over 220 minutes. Once the initiator feed was complete,an additional 19.4 g of Luperox® 7M75 initiator and 139.1 g of xylenewere fed over half an hour. The 12-liter flask was held at reflux for 1hour and cooled to 80° C. An additional 84.6 g of xylene were added tothe 12-liter flask and the batch filled out.

The resulting copolymer@ 64.7% solids had a GPC Mn of 2683 and GPC Mw of3386. The copolymer had an average number of 2.6 hydroxyl groups fromthe hydroxyethyl acrylate per polymer chain. The Tg of the copolymer was25.6° C., using dynamic scanning calorimetry.

Comparative Copolymer 1 (Comp. Copolymer 1)

To a five-liter flask fitted with heating mantle, stirrer, condenserwith 50 ml moisture receiver, nitrogen blanket, monomer and initiatorfeed lines, enough solvent (Aromatic 100 from ExxonMobil ChemicalChemical, Houston, Tex.) was added to completely fill the receiver.Then, 300.1 g of solvent (Aromatic 100) was added to the reaction flaskand the flask was heated to reflux, followed by the addition of amonomer mixture consisting of 551.1 g of hydroxyethylmethacrylate(Rocryl® 400 monomer from Rohm and Haas Company, Philadelphia, Pa.) and9459 isobornyl acrylate (Sipomer® HP from Rhodia Inc., Cranbury, N.J.)over a period of 240 minutes to the flask. Simultaneously with themonomer feed, an initiator feed consisting of 45 g of tertiarybutylperoxyacetate (Luperox® 7M75 from Atofina, Philadelphia, Pa.) and 250.1g of Aromatic 100 was added over a period of 270 minutes. Reflux at atemperature of approximately 169° C. was maintained over the entirereaction time. After completion of the initiator feed, the flask wascooled to 150° C. and 250.2 g of methyl N-amyl ketone (PM133 fromEastman Chemical, Kingsport, Tenn.) was added. The flask was furthercooled to less than 80° C. and the contents poured out. The resultingcopolymer (HEMA/IBOA//37/63) was at 70% solids, with a GPC Mn of 1637,and GPC Mw of 2978 using polystyrene as the standard. The average numberof functionalities (hydroxyl) was 4.6 per polymer chain and the Tg ofthe copolymer was 41.05° C.

Comparative Copolymer 2 (Comp. Copolymer 2)

To a 2-liter flask fitted with an agitator, water condenser,thermocouple, nitrogen inlet, heating mantle, and addition pumps andports was added 305.3 g of xylene, which was agitated and heated toreflux temperature (137 to 142° C.). A monomer mixture comprising of106.1 grams styrene, 141.4 grams methyl methacrylate, 318.3 gramsisobutyl methacrylate, 141.4 grams hydroxyethyl methacrylate and 10.4 gxylene was then added to the flask via the addition pumps and portssimultaneously with an initiator mixture comprising 17.0 grams t-butylperacetate and 85.2 g xylene. The monomer mixture was added over 180minutes and the addition time for the initiator mixture was also 180minutes. The batch was held at reflux (137° C. to 142° C.) throughoutthe polymerization process. An initiator mixture comprising of 4.3 gt-butyl peracetate and 57.8 g of methyl ethyl ketone was thenimmediately added to the reaction mixture over 60 minutes and the batchwas subsequently held at reflux for 60 minutes. The batch was thencooled to below 90° C. and 13.0 g of methyl ethyl ketone were added. Theresulting polymer solution has weight solids of 60% and viscosity of14,400 cps. The number average molecular weight of the resulting hydroxyfunctional acrylic copolymer was 5,000 and weight average molecularweight was 11,000, as determined by gel permeation chromatography(polystyrene standard).

Clear coating composition of the invention (Examples 1 through 5 andComparative Examples 1 and 2) were prepared by adding the componentslisted in Table 1 below (all in parts by weight): TABLE 1 Comp. Comp.Composition Components Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2 CrosslinkableComponent Copolymer 3 43.71 Copolymer 4 43.63 Copolymer 5 44.32 Comp.Compound 1* 22.39 Comp. Copolymer 1 36.83 Solvent (butyl Acetate) 4.614.69 3.69 11.39 7.93 Flow Additive** 0.58 0.58 0.59 0.32 0.51Catalyst*** 2.90 2.90 2.93 1.62 2.56 Crosslinking Component Tolonate ®HDT - LV 14.27 14.27 14.27 14.27 14.27 (Isocyanurate Trimer ofHexamethylene Diisocyanate)*****Comp. Copolymer (Reactive oligomer based on procedure # 2 in U.S. Pat.No. 6,221,494 B1) @ 80% weight solids in Methyl Amyl Ketone.**10% BYK ® 301 Flow Additive from BYK-Chemie, Wallingford, Connecticutin propylene glycol monomethyl ether acetate.***1% Di Butyl Tin Dilaurate in Methyl Ethyl Ketone.****Supplied by Rhodia Chemicals, Inc., Cranbury, New Jersey.

The crosslinkable and crosslinking components listed in Table 1 abovewere mixed to form pot mixes, which were applied with a doctor bladeover a separate phosphated cold roll steel panels primed with a layer ofPowerCron® Primer supplied by PPG, Pittsburgh, Pa., to a dry coatingthickness of 50 micrometers and air dried at ambient temperatureconditions. Then the panels were tested using the tests set forth infollowing Table 2, which also includes the test results: TABLE 2 Comp.Comp. Ex. 1 Ex. 2 Ex 1. Ex. 2 Ex. 3 PE/MH/ IBOA/ IBOMA/ MMA/ MMA/ EOHEMA HEA HEA HEA Properties & Tests 964 70/30 70/30 70/30 70/30 GPC Mn1054 1684 1935 2683 2683 GPC Mw 4.6 2893 2656 4198 3386 Tg 60 43.3 38.627.1 25.6 Viscosity @ 60% 242 200 135 710 450 Theoretical Solids (cps)Equivalent Weight 55 433 396 394 320 Pot Life in minutes 385 95 94 76 85BK3 Time in 255 231 111 83 83 minutes Cotton Tack Free 255 240 180 262Time in minutes Persoz Hardness 16 41 24 24 26 (pz) 4 Hours @ Room Temp.1 day @ Room 123 178 145 105 113 Temp. Visual Appearance Good Good GoodGood Good Fisher Hardness (FI)  1 day 15.8 19 28 23 27 30 days 59 172115 75 82 30 days @ 3 mil 58 82 68 18 15 Water Spot Test - 4 7 8 8 9 8hours @ Room Temp. Swell Ratio  1 day 1.99 1.83 1.86 1.63 1.68 30 days1.61 1.63 1.58 1.57 1.65 Gel Fraction - 30 99.9 94.4 91.1 92.3 91.6 day@ Room Temp.*The viscosity of copolymers.

In general the results of Table 2 show that the properties of Examples1, 2 and 3 are comparable to the properties of Comparative Example 2.However, the results of Table 2 show that the properties of Examples 1,2 and 3 show improved coating properties over that of ComparativeExample 1.

The improved coating hardness and coating cure times provided by thecoating compositions of the present invention over those provided by thecoating compositions using functional oligomer Comparative Compound 1will permit refinish body shops to sand and buff the clearcoats muchearlier, thereby improving the body shop productivity. Moreover, theseimproved properties also allow a refinish formulator to include higheramounts of these copolymers in refinish coating compositions, therebyreducing the VOC in the resulting coating compositions without adverselyaffecting the coating properties.

Viscosity Test Comparison

Copolymers 3, 4, 5 and Comparative Copolymer 2 were reduced to 60%weight solids with a solvent blend of 80% Methyl amyl Ketone and 20%Methyl ethyl ketone. The results, shown in the Table 2, indicate thatthe viscosities of copolymers 1, 2 and 3 are much lower than those of aconventional acrylic copolymer, such as Comparative Copolymer 2, whichhad a viscosity at 60% solids of 14,400 cps.

Thus, it is clearly seen from the property and viscosity data of thecopolymers of the present invention and the coating compositions madetherefrom that these types of copolymers offer a significant advantagein lowering VOC as compared to conventional acrylic copolymers.Furthermore, the copolymers of the present invention also providefavorable film forming properties (early and final) when comparedagainst the oligomers such as those described in # U.S. Pat. No.6,221,494 B1.

1. A coating composition comprising crosslinkable and crosslinkingcomponents, wherein said crosslinkable component comprises: a copolymerhaving on an average 2 to 25 crosslinkable groups selected from thegroup consisting of hydroxyl, acetoacetoxy, carboxyl, epoxy, primary andsecondary amine, and a combination thereof; a weight average molecularweight ranging from about 1000 to 4500; a polydispersity ranging fromabout 1.05 to 2.5; wherein said copolymer is polymerized from a monomermixture comprising one or more non-functional methacrylate monomers andone or more functional acrylate monomers provided with said functionalgroups, and wherein said crosslinking component for said crosslinkablegroups is selected from the group consisting of polyisocyanate,polyamine,. ketimine, melamine, epoxy, polyacid and a combinationthereof.
 2. The coating composition of claim 1 wherein when saidcopolymer has said acetoacetoxy functional groups said crosslinkingcomponent is ketimine or polyamine.
 3. The coating composition of claim1 wherein when said copolymer has said hydroxyl functional groups saidcrosslinking component is polyisocyanate.
 4. The coating composition ofclaim 1 wherein when said copolymer has said epoxy functional groupssaid crosslinking component is polyacid.
 5. The coating composition ofclaim 1 wherein said non-functional methacrylate monomer is providedwith a non-functional group selected from the group consisting of linearC₁ to C₂₀ alkyl, branched C₃ to C₂₀ alkyl, cyclic C₃ to C₂₀ alkyl,aromatic with 2 to 3 rings, phenyl and C₁ to C₂₀ fluorocarbon.
 6. Thecoating composition of claim 1 wherein said copolymer has a Tg rangingfrom about −10° C. to 80° C.
 7. The coating composition of claim 1wherein said composition has a VOC ranging from 0.1 kilograms to 0.72kilograms per liter.
 8. The coating composition of claim 1 wherein saidpolyisocyanate is provided within the range of 2 to 10 isocyanatefunctionalities.
 9. The coating composition of claim 1 wherein saidcrosslinkable component further comprises a catalyst selected from thegroup consisting of a tin compound, tertiary amine, acid catalyst and acombination thereof.
 10. The coating composition of claim 1 wherein saidcomposition is a clear coating composition, pigmented composition,metallized coating composition, basecoat composition, monocoatcomposition or a primer.
 11. The coating composition of claim 1 whereinsaid monomer mixture further comprises acid monomers.
 12. The coatingcomposition of claim 1 wherein said copolymer is provided with silanefunctionalities by post reacting said copolymer having said hydroxylfunctionalities with isocyanatopropyl trimethoxy silane.
 13. The coatingcomposition of claim 1 wherein said monomer mixture further comprises0.01% to 10% by weight of functional acrylate monomers.
 14. The coatingcomposition of claim 1 wherein said monomer mixture further comprises0.01% to 10% by weight of non-functional methacrylate monomers.
 15. Thecomposition of claim 1 wherein said crosslinkable component furthercomprises 0.1 weight percent to 95 weight percent based on the totalweight of the crosslinkable component of an acrylic polymer, apolyester, reactive oligomer, non-alicylic oligomer or a combinationthereof.
 16. The composition of claim 1 wherein said crosslinkablecomponent further comprises 0.1 to 50 weight percent of a dispersedacrylic polymer, the percentage being based on the total weight of thecomposition solids.
 17. The composition of claim 1 further comprises analdimine, polyaspartic ester or a combination thereof.
 18. The coatingcomposition of claim 1 wherein said copolymer is produced by freeradical polymerization of said monomer mixture at a polymerizationtemperature ranging from about 120° C. to 300° C.
 19. The coatingcomposition of claim 16 wherein a ratio of said non-functionalmethacrylate monomers to said functional acrylate monomers in saidmixture ranges from about 90:10::10:90.
 20. The coating composition ofclaim 19 wherein total amount of said non-functional methacrylatemonomers and said functional acrylate monomers in said monomer mixtureranges from about 100 percent to about 60 percent based on the totalweight of said monomer mixture.
 21. The coating composition of claim 19wherein said free radical polymerization takes place at a reactor gagepressure ranging from 0.1 to 3.5 MPa.
 22. A process for producing acoating on a substrate, said process comprises: a) mixing acrosslinkable and crosslinking components of a coating composition toform a potmix, wherein said crosslinkable component comprises: acopolymer having on an average 2 to 25 crosslinkable groups selectedfrom the group consisting of hydroxyl, acetoacetoxy, carboxyl, epoxy,primary and secondary amine, and a combination thereof; a weight averagemolecular weight ranging from about 1000 to 4500; a polydispersityranging from about 1.05 to 2.5; wherein said copolymer is polymerizedfrom a monomer mixture comprising one or more non-functionalmethacrylate monomers and one or more functional acrylate monomersprovided with said functional groups, and wherein said crosslinkingcomponent for said crosslinkable groups is selected from the groupconsisting of polyisocyanate, polyamine, ketimine, melamine, epoxy,polyacid and a combination thereof; b) applying a layer of said potmixon said substrate; c) curing said layer into said coating on saidsubstrate.
 23. The process of claim 22 further comprising air dryingsaid layer after said application step.
 24. The process of claim 22 or23 wherein said curing step at temperatures ranging from ambient to 204°C.
 25. The process of claim 22 wherein said substrate is an automotivebody.